public class Demo4 {
    public int count = 0;
    synchronized public void increase(){
        count++;
    }
    public static void main(String[] args) throws InterruptedException {
        Demo4 demo = new Demo4();
        Thread t1 = new Thread(() -> {
            for(int i = 0; i < 10000; i++){
                demo.increase();
            }
        });
        Thread t2 = new Thread(() -> {
            for(int i = 0; i < 10000; i++){
                demo.increase();
            }
        });
        t1.start();
        t2.start();
        t1.join();
        t2.join();
        System.out.println("count = " + demo.count);
    }
}
